There is a known polarizer, obtained on the basis of liquid-crystal solutions of organic dyes [1]. Polarizer, according to the herein technology, is obtained by application of thin film of liquid crystalline dye solution onto a glass or polymer substrate via one of the known methods. The distinction of this technology lies in that the orientation of the dye molecules occurs in the process of application of the film, so that a thin heat-resistant polarizing coating forms on the substrate immediately after drying. Such films could be used as polarizers in various optical devices. Their application allows creation of new designs of liquid-crystal displays, in which polarizers could form directly on the surface of liquid crystal cell, on the outside as well as on the inside.
Application of polarizers in displays bears certain peculiarities, related to their small thickness and hydroscopicity, as well as to the contemporary techniques of display manufacturing. Thus, for example, in case of external positioning of polarizers, they have to be protected by some means to prevent their mechanical damage. Moreover, the area, covered by the protective layer, should be larger than the area of the polarizer in order to completely avoid any contact of the polarizer with the surroundings and prevent penetration of moisture. In case of their placement inside the cell, polarizer should not be around the perimeter of the cell at the areas of adhering since it will compromise the quality of the adherence for once, and will contact with the surroundings, second. Therefore, polarizer should cover only the working area of the display and should not be at its peripherals. Taking into account that several displays are formed on a single substrate, a necessity to form a pattern on its surface arises. This could be performed by localized application of polarizer onto the substrate, or by the localized removal of the polarizing layer applied previously on the entire area of the substrate, preserving it on the proper regions of the substrate.
Various methods of application of the herein films and machinery allowing its implementation are known [2]. Application of LC solution could be implemented using slot, rod or roller. However, the known apparatuses do not allow obtaining polarizers with reproducible characteristics because of the difficulties of forming a uniform 15–10 μm thickness wet layer film without lines and with uniform orientation of molecules over the entire working field of the substrate. Besides that, these apparatuses do not allow obtaining polarizers with polarizing layer applied on separate regions of the substrate.
There are known methods of forming a pattern of polarizing films based on lyotropic liquid crystal (LLC) compounds [3]. According to [3], the film is formed by a cylindrical engraved roller, in which the engraving is implemented as grooves on the surface of the roller within the boundaries of the pattern. The grooves get filled with LLC solution, which subsequently is transferred onto the surface of the substrate via rolling the roller over it. This method has the disadvantage that due to the high viscosity of the LLC, a roller with the diameter of no larger than 3 cm can be used to ensure quality of application. Therefore it is difficult to form patterns with linear dimensions along the direction of application larger than 10 cm. Besides that, the use of this method strongly depends on viscosity of LLC and the thickness of the forming film. In particular, the degree of orientation of molecules in thick films appears to be substantially worse than in thin ones. Therefore, in order to form a pattern on a polarizer, it is favorable to apply a layer of polarizer on the entire area of the substrate and later locally remove it from a part of the area, leaving the proper configuration of the polarizer.
Various methods of removing thin isotropic films from the surface of a substrate are known, either through mechanical removal on separate areas or using protective mask via etching [4]. However, all of them have a number of substantial disadvantages, which limit their applicability for removal of polarizing layers. In particular, the mechanical method requires frequent replacement or cleaning of the removed material from the working element, and constant evacuation of the dust formed in the process of operation. The methods of local removal of polarizing layer via etching or rinsing with the use of protective mask are less productive and more expensive since they include several additional technological stages, related to formation of the protective mask. Besides that, the application of the protective mask onto the polarizing layer and its subsequent removal invariably leads to worsening of the polarizer's structure.